Wyoming Private Well Water Quality 2026

Wyoming’s Geology Is the Primary Threat to Well Water

Wyoming sits atop some of the most mineralogically complex geology in the United States. The same rock formations that have made the state one of the country’s most important sources of uranium, coal, and oil and gas are also a direct source of groundwater contamination for private well owners. Uranium, arsenic, selenium, radium, and radon all occur naturally in Wyoming’s aquifers — not as the result of industrial accidents, but as a consequence of the geology through which groundwater moves.

The Wyoming Department of Environmental Quality (WDEQ) explicitly lists uranium, radium, selenium, and methane among the most common contaminants found in Wyoming groundwater — alongside the more familiar bacteria, nitrate, and arsenic. This places Wyoming in a different category from many other states, where the primary well water threat is industrial or agricultural in origin. In Wyoming, the ground itself is the hazard.

None of these naturally occurring contaminants can be seen, smelled, or tasted at dangerous concentrations. The WDEQ’s Know Your Well programme recommends that all private well owners test for arsenic, uranium, radium, and selenium — in addition to annual testing for bacteria and nitrate — because the presence of these contaminants is genuinely unpredictable. Wells located close to each other can produce water with dramatically different contamination profiles depending on the specific geology at depth.

The federal MCL for uranium in drinking water is 30 micrograms per litre (µg/L). For arsenic, the standard is 10 µg/L. Long-term exposure to uranium above the MCL is associated with kidney damage. Long-term arsenic exposure is linked to cancers of the skin, bladder, and lung, as well as cardiovascular disease and type 2 diabetes.

Uranium Mining Legacy and Groundwater

Wyoming holds the largest known uranium ore reserves in the United States and has historically ranked No. 1 in national uranium production. As of 2025, it is the No. 2 producing state (behind Utah, having recently surpassed Texas), with industry analysts projecting it will reclaim top spot as new facilities come online. The legacy of decades of conventional and in-situ recovery (ISR) uranium mining has left a documented groundwater contamination footprint across the state. The WDEQ Groundwater Section has an entire programme dedicated to developing groundwater classifications for aquifers impacted by in-situ uranium mining operations.

The Powder River Basin in northeast Wyoming and the Gas Hills area of Fremont County are among the regions with the highest historical uranium mining activity. Research published in connection with the Pavillion, Wyoming fracking contamination investigation found arsenic and uranium in domestic drinking water wells at levels higher than would be expected from natural sources alone — a reminder that industrial activity compounds an already elevated baseline risk.

In-situ uranium recovery — the dominant modern mining method — injects chemical solutions underground to dissolve uranium from ore, then pumps the uranium-bearing solution to the surface. Despite restoration requirements, restoring affected aquifers to pre-mining standards has proven technically difficult, and WDEQ actively oversees restoration monitoring at active and former ISR sites.

PFAS from Military Sites and Airports

F.E. Warren Air Force Base, located immediately west of Cheyenne in Laramie County, has been identified as a PFAS investigation site. The base’s Fire Protection Training Areas 1 and 2 are under examination for potential PFAS contamination from historical use of aqueous film-forming foam (AFFF), and WDEQ is working with federal partners on ongoing remediation. Groundwater and soil contamination at the base was first discovered in the 1980s — the PFAS investigation is the most recent chapter in a longer contamination history.

The Wyoming Air National Guard has been remedying contamination at the Cheyenne Municipal Airport since 2001. In June 2024, the Jackson Hole Airport Board joined a multiparty federal lawsuit against manufacturers of PFAS-containing aviation firefighting foam, citing trace-level PFAS detections in the Snake River Aquifer near the airport — a source of drinking water for some area residents.

WDEQ has launched a PFAS in Drinking Water Monitoring Assistance Programme, operating through contractor HydroGeoLogic (HGL), which offers free PFAS sampling and next-steps guidance to private well owners located near known or potential PFAS sources. There is no deadline for private well owners to enrol. This is one of the few proactive state programmes of its kind and represents a genuine resource for well owners in at-risk areas.

Oil and Gas: An Additional Risk for Rural Well Owners

Wyoming is a major oil and gas producing state, and spills, leaks, and improper disposal of produced water from drilling operations represent a documented contamination pathway for private wells. WDEQ’s Groundwater Pollution Control programme issues permits for coal bed methane produced water impoundments, with monitoring requirements specifically designed to detect potential shallow aquifer contamination — an acknowledgement that the risk is real and ongoing.

The Pavillion area of Fremont County became a flashpoint for the national debate about fracking and groundwater contamination after EPA draft findings identified compounds associated with hydraulic fracturing in domestic drinking water wells. While the final federal assessment stopped short of declaring widespread contamination, the Pavillion case established that fracking-related compounds — including arsenic and uranium at levels elevated above natural background — can be found in private drinking water wells in oil and gas country.

For well owners in or near Wyoming’s oil and gas basins — the Powder River Basin, the Wind River Basin, the Pinedale Anticline, or the Green River Basin — periodic testing for petroleum hydrocarbons, VOCs, arsenic, and uranium is prudent, particularly if drilling activity has occurred nearby.

Nitrate and Bacteria Risks

In agricultural areas and where livestock operations are concentrated, nitrate from fertiliser runoff and animal waste represents an ongoing risk to shallow wells. Bacteria contamination — including E. coli and total coliform — can occur when wellheads are improperly sealed, flood or surface water enters, or septic systems are positioned too close to well casings. WDEQ recommends annual testing for both bacteria and nitrates for all private well owners regardless of location.

Regulatory Situation for Wyoming Well Owners

Private residential wells in Wyoming are not regulated under the state’s water quality laws. There is no mandatory testing requirement, no notification system, and no requirement for periodic monitoring. The Wyoming State Engineer’s Office handles well permitting and construction oversight — contact them at 307-777-6150 — but once a well is operational, testing and treatment are entirely the well owner’s responsibility.

Wyoming has no state-level PFAS maximum contaminant limits for private wells. The federal PFAS MCLs (4 ppt for PFOA and PFOS individually) apply to public water systems only. WDEQ does offer the PFAS Monitoring Assistance Programme as a free resource for at-risk private well owners, but participation is voluntary. Contact WDEQ’s Know Your Well line at 307-777-WELL (9355) for guidance on testing and certified laboratories.

Check our Wyoming municipal water quality page for city-by-city tap water data, or use our live boil water notice tracker for active advisories statewide.

Known High-Risk Areas in Wyoming

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Wyoming Well Water — and What to Do Next

The WDEQ recommends a baseline inorganic panel for all Wyoming private well owners, covering arsenic, uranium, selenium, radium, lead, copper, iron, manganese, sulfate, and total dissolved solids, in addition to annual bacteria and nitrate testing. This reflects Wyoming’s unusual contamination profile: the state’s own regulatory agency acknowledges that the geology poses a routine risk that well owners need to actively manage.

Contact WDEQ’s Know Your Well programme at 307-777-WELL (9355) to find a certified laboratory and access contamination fact sheets specific to your region. If you are near a military site, airport, or oil and gas operation, ask specifically about PFAS testing and enquire whether you are eligible for the WDEQ PFAS Monitoring Assistance Programme’s free sampling service.

For filter options, our well water filter guide covers reverse osmosis systems for uranium, arsenic and PFAS, UV disinfection for bacteria, and whole-house well systems for comprehensive multi-contaminant treatment. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For other Rocky Mountain and Western well water risks, see our pages on Colorado wells and Montana wells. Return to the private well water directory to find your state.